Zusammenfassung, AbstractWe present measurements of amplified spontaneous emission (ASE) in films of spiro-sexipheryl and higher branched spiro, starburst compounds of the 1st and 2nd generation. Gain narrowing is observed at threshold intensities of approximately 3.2 muJ/cm 2 when pumped with 500 ps pulses at 337 nm. A comparison of ASE peak wavelengths, linewidths and degradation kinetics in air is presented for the different spiro, compounds. The ASE lines are the 1-0 fluorescence transitions of the three compounds at 419, 428 and 443 nm, respectively, with linewidths of approximately 3 nm. The dependence of ASE threshold on film thickness is explained in terms of waveguide optics. The lowest threshold is achieved for monomode films (100-150 nm). Photodegradation effects occur in air atmospheres but can be suppressed in oxygen-free environments. (C) 2002 Elsevier Science B.V. All rights reserved.